Sofa-sleepers generally comprise a four section foldable bed frame including pivotally interconnected head, body, intermediate and foot sections which are adapted to be folded between a fully folded or retracted position into a box-like sofa frame, and an extended position wherein the sections extend out and over the front rail of the sofa frame to form a bad. The head, body, intermediate and foot sections of the bed frame each include a pair of opposed side rails or members which are pivotally connected at their ends so that the sections are foldable or collapsible upon one another. The head and foot sections of the bed frame have end rails or members extending between the side rails. The side rails support a deck comprising a wire frame or link fabric or sheet of woven polypropylene or other plastic material over which a mattress is placed for sleeping. U.S. Pat. No. 4,752,976 issued to the assignee of the present application discloses a woven polypropylene fabric deck secured directly to the side rails of the bed frame. The bed frame is supported vertically when in an extended bed position by a plurality of foldable legs which fold or pivot into a collapsed position against the foldable bed frame when the bed frame is retracted.
When a user lies on a mattress supported by the bed frame in its extended position, a heavy load is placed on the deck, particularly in the area of the user's head and shoulders. This load exerts an inwardly directed force on the side rails of the head and body sections of the bed frame. This inwardly directed force tends to urge the side rails of the head and body sections towards each other, creating stress on the side rails and if great enough may even bend the side rails.
To alleviate such stresses, in prior art sofa beds, a lateral cross brace is typically connected between the side rails of the body section of the bed frame at a location where the chest and shoulders contact the deck. The cross brace is welded or riveted in a fixed position to the side rails in substantially the same horizontal plane as the upper surface of the bed frame, just beneath the deck and mattress of the sofa bed which are supported by the side rails of the bed frame. It has bean found that even with a relatively thick mattress the chest and shoulders are heavy enough to push downwardly and engage the cross brace when it is positioned just beneath the link fabric. Contact with the cross brace at the shoulders or chest is very uncomfortable and makes it difficult to obtain a restful night's sleep.
In order to avoid this problem, the lateral cross braces in some prior art sofa-sleepers have been formed with a crown or bow from end to end so that the middle portion of the cross brace is disposed approximately one inch below the deck secured to the side rails of the bed frame. This has proved to be unsatisfactory because cross braces with only about a one inch bow can still be felt by persons lying down on the deck when the sofa bed frame is extended.
In order to avoid contact of the chest and shoulders with a lateral cross brace, it is necessary to dispose the cross brace at least about three inches beneath the deck secured to the side rails of the bed frame. In accordance with the teachings of the prior art, however, it is not possible to design a sofa-sleeper bed with a cross brace having a three inch bow which is welded or riveted in a fixed position at each and to the side rails. This is because the foldable sections of the bed frame must be permitted to collapse in a compact unit for insertion within the box-like sofa frame of the sofa-sleeper. A fixed cross brace extending three or more inches below the deck secured to the side rails of the bed frame would not clear the front of the box-like sofa frame as the foldable bed frame sections are collapsed therein. Even if the sofa frame were designed to avoid interference with the lateral cross brace, it would contact the floor when the bed frame sections are collapsed into the sofa frame unless the sofa frame was raised a proportional distance from the floor. Raising the height of the sofa seat is not an acceptable design alternative since it must be low enough to permit persons of average height to touch the floor when seated.
U.S. Pat. No. 4,571,755 also issued to the assignee of the present application discloses a U-shaped cross brace which is pivotally mounted to the side rails of the body section of the bed frame. However, when the bed frame is extended, this cross brace is adapted to be disposed in a lowered position in which the bottom or transverse tube of the U-shaped cross brace is parallel to and approximately three inches below the horizontal plane defined by the bed frame. A complex linkage mechanism is required to pivot the U-shaped cross brace into a folded position in which the legs of the cross brace are substantially parallel to rather than transverse to the bed frame side rails so that the sofa sleeper frame may be placed into the sofa frame. The complex linkage mechanism required to fold the U-shaped cross brace into a folded position is expensive and increases the cost of the sofa sleeper.
Therefore, it has been one objective of the present invention to provide a sofa sleeper foldable sofa bed assembly having at least one U-shaped cross brace which may be raised quickly and easily without the assistance of a complex linkage mechanism.
It has been a further objective of the present invention to provide a sofa sleeper foldable sofa bed assembly having at least one U-shaped cross brace which is biased in a raised position so as to enable the sofa bed assembly to be folded into a sofa frame quickly and easily.